This project has the ultimate goal of determining the relative contribution of different factors in infection and reinfection of schistosomiasis and soil transmitted helminths (STH) to improve current strategies for control of these parasites. Schistosomiasis and STH are widespread parasitic infections posing an enormous toll on the socioeconomic development. An estimated 2 billion people are affected by those parasites. Studies of the extent of multiple infections and the impact they have on each other in terms of both susceptibility to infection and disease outcomes are important for control programs that consider the use of chemotherapy and vaccination jointly. As resources available for control are often limited, it is essential to know the distribution of schistosomiasis at the micro-level to devise optimal intervention strategies for targeting high- risk population. We believe that a spatial approach can lead to identification of complex interactions among host genetic, immunological, and behavioral characteristics, the environment, and other factors that determine the pattern of infection and disease in human populations. Therefore the proposed project will test 3 general hypothesis: 1 )that spatial distributions of S. mansoni and STHs infections and reinfection following PZQ and albendazol treatment are not random but heterogeneous at the individual, household and community levels;2)that spatial distribution of the above parasites is associated with demographic, immunological, genetic, socioeconomic and human behavior parameters and 3)that the treatment program will have a varying impact across groups and households located at different distances from potential transmission sites and from sited with different transmission potential. The geospatial clusters of infection after the treatment program will be significantly different from the pre-infection clusters. In the process of testing these hypothesis we will compare the spatial distribution of helminths individually and at households evels before treatment and one year after treatment and analyzed with data we already have of prevalence, ntensity of infection, demographic, socioeconomic, water contact patterns, genetic and immunological actors. We will also collect data related to those variables 2 years after the second treatment using the same methods. The approach used in this pilot study, including modeling efforts of multi-parasite infection and re-infection with a chemotherapy intervention, may be tested in other rural areas.